Fiber-optic communication systems are widely used for transmitting a high volume of voice, video and data information over medium to large distances. These systems typically include complex equipment that aggregates multiple information streams from a plurality of customers or customer sites into high data rate signals, and transmits these high data rate signals over an optical fiber of a fiber-optic link.
To be transmitted over an optical link, the data has to be first converted from its original electrical format to an optical format by modulating a light source to form an optical signal. Data carried by the optical signal then must be converted back to an electrical format before it can be processed by a recipient, or routed by a routing device, such as a network switch. A number of protocols define the conversion of electrical signals to optical signals, transmission of those optical signals, and the reverse conversion into the electrical domain, including SONET, SDH, and the ANSI Fibre Channel (FC) protocol. These electro-optical and opto-electrical conversions at the ends of an optical link are typically implemented using transceiver or transponder modules. Each transceiver module typically contains a laser transmitter circuit capable of converting electrical signals to optical signals, and an optical receiver capable of converting received optical signals back into electrical signals. Transponders are transceivers that include electrical multiplexing and de-multiplexing functions, which are typically required in high bit rate transmission such as 10 Gb Ethernet, OC-192 (10 Gb/s) and OC-768 (40 Gb/s). Conventional optical transponders typically receive electrical signals in parallel, serialize the data represented by these signals, convert the serialized data into a light-based signal and couple that signal to an outbound optical fiber. Similarly, conventional optical transponders typically receive a serialized light-based data stream, convert that data stream to an electrical equivalent, de-serialize that data, and provide the de-serialized electrical data, i.e., data in a parallel format, to a plurality of output terminals. To ensure reliable communications with minimum loss of data, each of these internal transponder operations, as well as its overall performance, has to be precisely and automatically controlled and monitored.
Modem developments in optical communication networks impose contradictory requirements on the optoelectronic modules they employ. The wide variety of different types of networks where optical transponders and other optoelectronic modules are used, necessitates having a large variability in transponder characteristics. Furthermore, due to the proprietary nature of telecommunication systems used in optical networks, different customers often have differing requirements for particular aspects of the module design even when the modules are to be used in a similar type of application. These two factors, in combination with a relatively large number of system integrators operating in the market and a large number of sometimes competing transmission protocols, push the module manufacturers towards developing multiple modifications for each type of optoelectronic modules. On the other hand, interoperability requirements for modules from different manufacturers, as well as the need to reduce manufacturing and especially development cost of the modules, demand standardization of the transponder and other optoelectronic modules to a highest possible degree, especially with respect to their electrical and optical interfaces.
Efforts have been made to meet this seemingly contradictory requirements by adding certain amount of flexibility in the module's design, in particular their optical, i.e. the network-side, interface, for enabling their operation in different types of networks. For example, U.S. Pat. No. 5,956,168 in the names of Levinson et al. discloses a dual optical fiber transceiver having an on-board a microcontroller including a multi-protocol state machine for establishing a full duplex connection whenever the other device operates in compliance with either the Open Fiber Control (OFC) protocol or a standard “laser transmitter always on” protocol. Other optical transponders have been suggested and/or currently used in the art that are capable of operating at different data rates, by either automatically detecting the data rate of an incoming optical signal, or after receiving an external “rate change” control signal from the host device.
In addition to the network-side interface, a transceiver or transponder module is also electrically interfaced with a host device—such as a host computer, a shelf of a communication equipment rack, or a line card, via a compatible electrical connection port. The electrical interface with the host device, apart from providing electrical connections for passing the client data traffic to and from the transponder module, is also used by the host device to control and monitor many different aspects of the module's operation, thereby ensuring its reliable operation and conformity to the network's requirements. These control and monitor functions are carried out by means of a number of digital controls and status (C&S) signals, which can be exchanged between the host device and the module using either a serial bus connection, a multitude of discrete communication lines between the host and the module typically established using a multi-pin connector wherein each pin corresponds to a certain C&S signal, or both.
To improve interoperability between optical transponders from different manufacturers, various multiple source agreements (MSA) have been adopted by transponder manufacturers, defining basic features of the transponder electrical interfaces, including the C&S interface. For example, a group of leading optical manufacturers developed a set of standards for 10 Gb/s and 40 Gb/s optical transponder modules called the 300PIN MSA for 10 and 40 Gigabit Transponders, which specifies a set of C&S signals to be supported by the transponders, and their pin allocations for the module's 300 pin connector. Other standards and MSAs may exist that define alternative connector and C&S signal configurations.
The existent industry standards and MSAs allow for a considerable degree of freedom in implementing the C&S signals they specify. This freedom allows module manufacturers to provide MSA-compliant transponders having differing means for generating the MSA-defined C&S signals and differing configurations of the C&S interface, thereby enabling them to satisfy varying requirements of particular system integrators for their specific systems and applications. Some customers may also decide to use non-MSA compliant transponders, or substitute some of the MSA-defined C&S signals with other signals per their system's requirements.
However, currently existing optoelectronic modules, such as optical transponders, have insufficient flexibility of the C&S interface, so that variations in customer and system requirements thereto often necessitate making changes in the module's printed circuit board design. In particular, existing optoelectronic modules with multi-pin connectors in which the C&S signals are individually routed from/to their respective pins within the module, such as the 300PIN MSA-compliant transponders, typically require a new circuit board design whenever a different routing of the C&S signals in the module is needed. Therefore, in the heretofore existing transponders, the customer-driven C&S interface variability has often been accomplished at the expense of longer transponders' development cycle and higher transponder cost.
It is therefore an object of the present invention to provide an optoelectronic module having a flexible C&S interface that can be reconfigured without hardware and circuit board changes.
It is another object of the present invention to provide an optical transponder or transceiver module for fiber-optic communication systems having a C&S interface to a host device formed by a plurality of pins of a multi-pin connector of the module, wherein the pin assignments to C&S signals can be reconfigured by downloading a different set of software instructions without hardware and printed circuit board changes.